In general, wounds and lesions can be divided into two types: acute and chronic. In cases where a wound is not initially surgically closed (delayed primary closure), the wound is left open for a time sufficient to allow the inflammatory process and angiogenesis to begin before surgical closure. Wounds healing by secondary intention are usually not amenable to surgical closure. As a result, the wound is left to granulate and epithelialize from the wound bed and edges. Numerous dressing products were developed during the past few years to accelerate this type of healing process.
For these types of acute wounds, occlusive dressings increase re-epithelialization rates by 30% to 50% and collagen synthesis by 20% to 60% compared to wounds exposed to air by providing an optimal healing environment that exposes the wound continuously to the surrounding fluid of proteinases, chemotactic factors, complements, and growth factors. An electrical gradient that may stimulate fibroblast and epithelial cell migration is maintained. The use of non-adherent dressing prevents the stripping of the newly formed epithelial layer.
An occlusive dressing is generally divided into a hydrating layer (antibiotic ointments or petrolatum jelly), a nonadherent contact layer, an absorbent and cushioning layer (gauze), and a securing layer (tape or wrap). Occlusive dressings are commonly applied within 2 hours of wounding and left on for at least 24 hours, rarely as long as 48 hours, for optimal healing of acute wounds. Initial wound hypoxia is important for fibroblast proliferation and angiogenesis; however, continued hypoxia at the wound site delays wound healing. As a result, if an occlusive dressing is applied to an ischemic wound, healing is severely impaired.
Chronic wounds are defined as wounds that fail to heal after 3 months. Venous stasis ulcers, diabetic ulcers, pressure ulcers, and ischemic ulcers are the most common chronic wounds. Many of the dressing options that attempt to heal venous stasis ulcers are a variation on the classic paste compression bandage, Unna's boot. These wounds can sometimes have large amounts of exudates that require frequent debridement. Alginates, foams, and other absorptives can be used in this situation. Because chronic wounds heal by slightly different mechanisms than those of acute wounds, experimentation with growth factors is being investigated. Regranex® and Procuren® (Curative Health Services, Inc., Hauppauge, N.Y.) are the only medications approved by the US Food and Drug Administration (FDA).
Despite these advances in the art, a need exists in the art for new and better methods and devices for restoring the natural process of wound healing at a lesion, the repair of which requires tissue remodeling and restoration.